This invention relates generally to radio-frequency (RF) antennas and, more particularly, to RF lens type antennas. Optical lens principles have been applied to RF antennas, either as an alternative to or in conjunction with reflective antennas. In simple terms, an RF lens comprises an array of elements that function as waveguides and provide regions of different propagation velocity for incident RF radiation. Therefore, an RF beam is refracted by the lens and can be selectively focused and/or steered as desired. RF lens type antennas have long been recognized for their advantages of high gain and very good interference rejection, but are also known to suffer from significant drawbacks. Specifically, RF lens antennas typically have a narrow instantaneous bandwidth, are limited to a handling single beam, and have a direction and frequency that are fixed by the specific hardware implementation of the lens. Unfortunately, these drawbacks are extremely significant in many fields of application, such as signals intelligence (SIGINT) and electronic warfare (EW) systems, which involve processing signals from multiple beams of different frequencies, scattered over a wide field of view and susceptible to the effects of jamming and interfering signals.
Therefore, there is a need for an RF lens type antenna that does not suffer from these drawbacks. In particular, there is a need for an RF lens type antenna that can handle multiple beams simultaneously, is not as limited in bandwidth, and can steer beams as desired, without being limited to particular hardware configurations. Ideally, it would be highly desirable to provide an RF lens type antenna that was adjustable in as near as possible to real time, to adapt rapidly to changing signal conditions. The present invention is directed to these ends.